/* Linear Loop transforms
- Copyright (C) 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009, 2010
+ Free Software Foundation, Inc.
Contributed by Daniel Berlin <dberlin@dberlin.org>.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
-Software Foundation; either version 2, or (at your option) any later
+Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
-#include "errors.h"
-#include "ggc.h"
#include "tree.h"
-#include "target.h"
-
-#include "rtl.h"
#include "basic-block.h"
#include "diagnostic.h"
+#include "obstack.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "timevar.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "tree-pass.h"
-#include "varray.h"
#include "lambda.h"
/* Linear loop transforms include any composition of interchange,
scaling, skewing, and reversal. They are used to change the
iteration order of loop nests in order to optimize data locality of
traversals, or remove dependences that prevent
- parallelization/vectorization/etc.
+ parallelization/vectorization/etc.
TODO: Determine reuse vectors/matrix and use it to determine optimal
transform matrix for locality purposes.
TODO: Completion of partial transforms. */
-/* Gather statistics for loop interchange. Initializes SUM the sum of
- all the data dependence distances carried by loop LOOP_NUMBER.
- NB_DEPS_NOT_CARRIED_BY_LOOP is initialized to the number of
- dependence relations for which the loop LOOP_NUMBER is not carrying
- any dependence. */
+/* Gather statistics for loop interchange. LOOP is the loop being
+ considered. The first loop in the considered loop nest is
+ FIRST_LOOP, and consequently, the index of the considered loop is
+ obtained by LOOP->DEPTH - FIRST_LOOP->DEPTH
+
+ Initializes:
+ - DEPENDENCE_STEPS the sum of all the data dependence distances
+ carried by loop LOOP,
+
+ - NB_DEPS_NOT_CARRIED_BY_LOOP the number of dependence relations
+ for which the loop LOOP is not carrying any dependence,
+
+ - ACCESS_STRIDES the sum of all the strides in LOOP.
+
+ Example: for the following loop,
+
+ | loop_1 runs 1335 times
+ | loop_2 runs 1335 times
+ | A[{{0, +, 1}_1, +, 1335}_2]
+ | B[{{0, +, 1}_1, +, 1335}_2]
+ | endloop_2
+ | A[{0, +, 1336}_1]
+ | endloop_1
+
+ gather_interchange_stats (in loop_1) will return
+ DEPENDENCE_STEPS = 3002
+ NB_DEPS_NOT_CARRIED_BY_LOOP = 5
+ ACCESS_STRIDES = 10694
+
+ gather_interchange_stats (in loop_2) will return
+ DEPENDENCE_STEPS = 3000
+ NB_DEPS_NOT_CARRIED_BY_LOOP = 7
+ ACCESS_STRIDES = 8010
+*/
static void
-gather_interchange_stats (varray_type dependence_relations,
- unsigned int loop_number,
- unsigned int *sum,
- unsigned int *nb_deps_not_carried_by_loop)
+gather_interchange_stats (VEC (ddr_p, heap) *dependence_relations ATTRIBUTE_UNUSED,
+ VEC (data_reference_p, heap) *datarefs ATTRIBUTE_UNUSED,
+ struct loop *loop ATTRIBUTE_UNUSED,
+ struct loop *first_loop ATTRIBUTE_UNUSED,
+ unsigned int *dependence_steps ATTRIBUTE_UNUSED,
+ unsigned int *nb_deps_not_carried_by_loop ATTRIBUTE_UNUSED,
+ double_int *access_strides ATTRIBUTE_UNUSED)
{
- unsigned int i;
+ unsigned int i, j;
+ struct data_dependence_relation *ddr;
+ struct data_reference *dr;
- *sum = 0;
+ *dependence_steps = 0;
*nb_deps_not_carried_by_loop = 0;
- for (i = 0; i < VARRAY_ACTIVE_SIZE (dependence_relations); i++)
+ *access_strides = double_int_zero;
+
+ for (i = 0; VEC_iterate (ddr_p, dependence_relations, i, ddr); i++)
{
- int dist;
- struct data_dependence_relation *ddr =
- (struct data_dependence_relation *)
- VARRAY_GENERIC_PTR (dependence_relations, i);
+ /* If we don't know anything about this dependence, or the distance
+ vector is NULL, or there is no dependence, then there is no reuse of
+ data. */
+ if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know
+ || DDR_ARE_DEPENDENT (ddr) == chrec_known
+ || DDR_NUM_DIST_VECTS (ddr) == 0)
+ continue;
- if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
+ for (j = 0; j < DDR_NUM_DIST_VECTS (ddr); j++)
{
- /* Some constants will need tweaking, but not something that should
- be user-accessible. Thus, no --param. */
- *sum += 100;
- continue;
+ int dist = DDR_DIST_VECT (ddr, j)[loop_depth (loop) - loop_depth (first_loop)];
+
+ if (dist == 0)
+ (*nb_deps_not_carried_by_loop) += 1;
+
+ else if (dist < 0)
+ (*dependence_steps) += -dist;
+
+ else
+ (*dependence_steps) += dist;
}
+ }
- /* When we know that there is no dependence, we know that there
- is no reuse of the data. */
- if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
+ /* Compute the access strides. */
+ for (i = 0; VEC_iterate (data_reference_p, datarefs, i, dr); i++)
+ {
+ unsigned int it;
+ tree ref = DR_REF (dr);
+ gimple stmt = DR_STMT (dr);
+ struct loop *stmt_loop = loop_containing_stmt (stmt);
+ struct loop *inner_loop = first_loop->inner;
+
+ if (inner_loop != stmt_loop
+ && !flow_loop_nested_p (inner_loop, stmt_loop))
+ continue;
+
+ for (it = 0; it < DR_NUM_DIMENSIONS (dr);
+ it++, ref = TREE_OPERAND (ref, 0))
{
- /* Ditto on the no --param here */
- *sum += 1000;
- continue;
- }
+ int num = am_vector_index_for_loop (DR_ACCESS_MATRIX (dr), loop->num);
+ int istride = AM_GET_ACCESS_MATRIX_ELEMENT (DR_ACCESS_MATRIX (dr), it, num);
+ tree array_size = TYPE_SIZE (TREE_TYPE (ref));
+ double_int dstride;
+
+ if (array_size == NULL_TREE
+ || TREE_CODE (array_size) != INTEGER_CST)
+ continue;
- dist = DDR_DIST_VECT (ddr)[loop_number];
- if (dist == 0)
- *nb_deps_not_carried_by_loop++;
- else if (dist < 0)
- *sum += -dist;
- else
- *sum += dist;
+ dstride = double_int_mul (tree_to_double_int (array_size),
+ shwi_to_double_int (istride));
+ (*access_strides) = double_int_add (*access_strides, dstride);
+ }
}
}
-/* Apply to TRANS any loop interchange that minimize inner loop steps.
- DEPTH is the depth of the loop nest, and DEPENDENCE_RELATIONS is an array
- of dependence relations.
+/* Attempt to apply interchange transformations to TRANS to maximize the
+ spatial and temporal locality of the loop.
Returns the new transform matrix. The smaller the reuse vector
- distances in the inner loops, the fewer the cache misses. */
+ distances in the inner loops, the fewer the cache misses.
+ FIRST_LOOP is the loop->num of the first loop in the analyzed loop
+ nest. */
+
static lambda_trans_matrix
-try_interchange_loops (lambda_trans_matrix trans,
- unsigned int depth,
- varray_type dependence_relations)
+try_interchange_loops (lambda_trans_matrix trans,
+ unsigned int depth,
+ VEC (ddr_p, heap) *dependence_relations,
+ VEC (data_reference_p, heap) *datarefs,
+ struct loop *first_loop)
{
- unsigned int loop_i, loop_j;
- unsigned int steps_i, steps_j;
+ bool res;
+ struct loop *loop_i;
+ struct loop *loop_j;
+ unsigned int dependence_steps_i, dependence_steps_j;
+ double_int access_strides_i, access_strides_j;
+ double_int small, large, nb_iter;
+ double_int l1_cache_size, l2_cache_size;
+ int cmp;
unsigned int nb_deps_not_carried_by_i, nb_deps_not_carried_by_j;
struct data_dependence_relation *ddr;
+ if (VEC_length (ddr_p, dependence_relations) == 0)
+ return trans;
+
/* When there is an unknown relation in the dependence_relations, we
know that it is no worth looking at this loop nest: give up. */
- ddr = (struct data_dependence_relation *)
- VARRAY_GENERIC_PTR (dependence_relations, 0);
+ ddr = VEC_index (ddr_p, dependence_relations, 0);
if (ddr == NULL || DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
return trans;
-
+
+ l1_cache_size = uhwi_to_double_int (L1_CACHE_SIZE * 1024);
+ l2_cache_size = uhwi_to_double_int (L2_CACHE_SIZE * 1024);
+
/* LOOP_I is always the outer loop. */
- for (loop_j = 1; loop_j < depth; loop_j++)
- for (loop_i = 0; loop_i < loop_j; loop_i++)
+ for (loop_j = first_loop->inner;
+ loop_j;
+ loop_j = loop_j->inner)
+ for (loop_i = first_loop;
+ loop_depth (loop_i) < loop_depth (loop_j);
+ loop_i = loop_i->inner)
{
- gather_interchange_stats (dependence_relations, loop_i, &steps_i,
- &nb_deps_not_carried_by_i);
- gather_interchange_stats (dependence_relations, loop_j, &steps_j,
- &nb_deps_not_carried_by_j);
-
+ gather_interchange_stats (dependence_relations, datarefs,
+ loop_i, first_loop,
+ &dependence_steps_i,
+ &nb_deps_not_carried_by_i,
+ &access_strides_i);
+ gather_interchange_stats (dependence_relations, datarefs,
+ loop_j, first_loop,
+ &dependence_steps_j,
+ &nb_deps_not_carried_by_j,
+ &access_strides_j);
+
/* Heuristics for loop interchange profitability:
- 1. Inner loops should have smallest steps.
- 2. Inner loops should contain more dependence relations not
- carried by the loop.
+
+ 0. Don't transform if the smallest stride is larger than
+ the L2 cache, or if the largest stride multiplied by the
+ number of iterations is smaller than the L1 cache.
+
+ 1. (spatial locality) Inner loops should have smallest
+ dependence steps.
+
+ 2. (spatial locality) Inner loops should contain more
+ dependence relations not carried by the loop.
+
+ 3. (temporal locality) Inner loops should have smallest
+ array access strides.
*/
- if (steps_i < steps_j
- || nb_deps_not_carried_by_i > nb_deps_not_carried_by_j)
+
+ cmp = double_int_ucmp (access_strides_i, access_strides_j);
+ small = cmp < 0 ? access_strides_i : access_strides_j;
+ large = cmp < 0 ? access_strides_j : access_strides_i;
+
+ if (double_int_ucmp (small, l2_cache_size) > 0)
+ continue;
+
+ res = cmp < 0 ?
+ estimated_loop_iterations (loop_j, false, &nb_iter):
+ estimated_loop_iterations (loop_i, false, &nb_iter);
+
+ if (res
+ && double_int_ucmp (double_int_mul (large, nb_iter),
+ l1_cache_size) < 0)
+ continue;
+
+ if (dependence_steps_i < dependence_steps_j
+ || nb_deps_not_carried_by_i > nb_deps_not_carried_by_j
+ || cmp < 0)
{
- lambda_matrix_row_exchange (LTM_MATRIX (trans), loop_i, loop_j);
-
+ lambda_matrix_row_exchange (LTM_MATRIX (trans),
+ loop_depth (loop_i) - loop_depth (first_loop),
+ loop_depth (loop_j) - loop_depth (first_loop));
/* Validate the resulting matrix. When the transformation
- is not valid, reverse to the previous matrix.
-
- FIXME: In this case of transformation it could be
- faster to verify the validity of the interchange
- without applying the transform to the matrix. But for
- the moment do it cleanly: this is just a prototype. */
+ is not valid, reverse to the previous transformation. */
if (!lambda_transform_legal_p (trans, depth, dependence_relations))
- lambda_matrix_row_exchange (LTM_MATRIX (trans), loop_i, loop_j);
+ lambda_matrix_row_exchange (LTM_MATRIX (trans),
+ loop_depth (loop_i) - loop_depth (first_loop),
+ loop_depth (loop_j) - loop_depth (first_loop));
}
}
-
+
return trans;
}
-/* Perform a set of linear transforms on LOOPS. */
+/* Return the number of nested loops in LOOP_NEST, or 0 if the loops
+ are not perfectly nested. */
+
+unsigned int
+perfect_loop_nest_depth (struct loop *loop_nest)
+{
+ struct loop *temp;
+ unsigned int depth = 1;
+
+ /* If it's not a loop nest, we don't want it. We also don't handle
+ sibling loops properly, which are loops of the following form:
+
+ | for (i = 0; i < 50; i++)
+ | {
+ | for (j = 0; j < 50; j++)
+ | {
+ | ...
+ | }
+ | for (j = 0; j < 50; j++)
+ | {
+ | ...
+ | }
+ | }
+ */
+
+ if (!loop_nest->inner || !single_exit (loop_nest))
+ return 0;
+
+ for (temp = loop_nest->inner; temp; temp = temp->inner)
+ {
+ /* If we have a sibling loop or multiple exit edges, jump ship. */
+ if (temp->next || !single_exit (temp))
+ return 0;
+
+ depth++;
+ }
+
+ return depth;
+}
+
+/* Perform a set of linear transforms on loops. */
void
-linear_transform_loops (struct loops *loops)
+linear_transform_loops (void)
{
- unsigned int i;
+ bool modified = false;
+ loop_iterator li;
+ VEC(tree,heap) *oldivs = NULL;
+ VEC(tree,heap) *invariants = NULL;
+ VEC(tree,heap) *lambda_parameters = NULL;
+ VEC(gimple,heap) *remove_ivs = VEC_alloc (gimple, heap, 3);
+ struct loop *loop_nest;
+ gimple oldiv_stmt;
+ unsigned i;
- for (i = 1; i < loops->num; i++)
+ FOR_EACH_LOOP (li, loop_nest, 0)
{
unsigned int depth = 0;
- varray_type datarefs;
- varray_type dependence_relations;
- struct loop *loop_nest = loops->parray[i];
- struct loop *temp;
- VEC (tree) *oldivs;
- VEC (tree) *invariants;
+ VEC (ddr_p, heap) *dependence_relations;
+ VEC (data_reference_p, heap) *datarefs;
+
lambda_loopnest before, after;
lambda_trans_matrix trans;
- bool problem = false;
- /* If it's not a loop nest, we don't want it.
- We also don't handle sibling loops properly,
- which are loops of the following form:
- for (i = 0; i < 50; i++)
- {
- for (j = 0; j < 50; j++)
- {
- ...
- }
- for (j = 0; j < 50; j++)
- {
- ...
- }
- } */
- if (!loop_nest->inner)
- continue;
- for (temp = loop_nest; temp; temp = temp->inner)
- {
- flow_loop_scan (temp, LOOP_ALL);
- /* If we have a sibling loop or multiple exit edges, jump ship. */
- if (temp->next || temp->num_exits != 1)
- {
- problem = true;
- break;
- }
- depth ++;
- }
- if (problem)
+ struct obstack lambda_obstack;
+ struct loop *loop;
+ VEC(loop_p,heap) *nest;
+
+ depth = perfect_loop_nest_depth (loop_nest);
+ if (depth == 0)
continue;
- /* Analyze data references and dependence relations using scev. */
-
- VARRAY_GENERIC_PTR_INIT (datarefs, 10, "datarefs");
- VARRAY_GENERIC_PTR_INIT (dependence_relations, 10,
- "dependence_relations");
-
-
- compute_data_dependences_for_loop (depth, loop_nest,
- &datarefs, &dependence_relations);
+ nest = VEC_alloc (loop_p, heap, 3);
+ for (loop = loop_nest; loop; loop = loop->inner)
+ VEC_safe_push (loop_p, heap, nest, loop);
+
+ gcc_obstack_init (&lambda_obstack);
+ VEC_truncate (tree, oldivs, 0);
+ VEC_truncate (tree, invariants, 0);
+ VEC_truncate (tree, lambda_parameters, 0);
+
+ datarefs = VEC_alloc (data_reference_p, heap, 10);
+ dependence_relations = VEC_alloc (ddr_p, heap, 10 * 10);
+ if (!compute_data_dependences_for_loop (loop_nest, true, &datarefs,
+ &dependence_relations))
+ goto free_and_continue;
+
+ lambda_collect_parameters (datarefs, &lambda_parameters);
+ if (!lambda_compute_access_matrices (datarefs, lambda_parameters,
+ nest, &lambda_obstack))
+ goto free_and_continue;
+
if (dump_file && (dump_flags & TDF_DETAILS))
- {
- unsigned int j;
- for (j = 0; j < VARRAY_ACTIVE_SIZE (dependence_relations); j++)
- {
- struct data_dependence_relation *ddr =
- (struct data_dependence_relation *)
- VARRAY_GENERIC_PTR (dependence_relations, j);
-
- if (DDR_ARE_DEPENDENT (ddr) == NULL_TREE)
- {
- fprintf (dump_file, "DISTANCE_V (");
- print_lambda_vector (dump_file, DDR_DIST_VECT (ddr),
- loops->num);
- fprintf (dump_file, ")\n");
- fprintf (dump_file, "DIRECTION_V (");
- print_lambda_vector (dump_file, DDR_DIR_VECT (ddr),
- loops->num);
- fprintf (dump_file, ")\n");
- }
- }
- fprintf (dump_file, "\n\n");
- }
+ dump_ddrs (dump_file, dependence_relations);
+
/* Build the transformation matrix. */
- trans = lambda_trans_matrix_new (depth, depth);
+ trans = lambda_trans_matrix_new (depth, depth, &lambda_obstack);
lambda_matrix_id (LTM_MATRIX (trans), depth);
- trans = try_interchange_loops (trans, depth, dependence_relations);
+ trans = try_interchange_loops (trans, depth, dependence_relations,
+ datarefs, loop_nest);
+
+ if (lambda_trans_matrix_id_p (trans))
+ {
+ if (dump_file)
+ fprintf (dump_file, "Won't transform loop. Optimal transform is the identity transform\n");
+ goto free_and_continue;
+ }
/* Check whether the transformation is legal. */
if (!lambda_transform_legal_p (trans, depth, dependence_relations))
{
if (dump_file)
fprintf (dump_file, "Can't transform loop, transform is illegal:\n");
- continue;
+ goto free_and_continue;
}
- before = gcc_loopnest_to_lambda_loopnest (loop_nest, &oldivs,
- &invariants);
+
+ before = gcc_loopnest_to_lambda_loopnest (loop_nest, &oldivs,
+ &invariants, &lambda_obstack);
+
if (!before)
- continue;
-
+ goto free_and_continue;
+
if (dump_file)
{
fprintf (dump_file, "Before:\n");
print_lambda_loopnest (dump_file, before, 'i');
}
-
- after = lambda_loopnest_transform (before, trans);
+
+ after = lambda_loopnest_transform (before, trans, &lambda_obstack);
+
if (dump_file)
{
fprintf (dump_file, "After:\n");
print_lambda_loopnest (dump_file, after, 'u');
}
+
lambda_loopnest_to_gcc_loopnest (loop_nest, oldivs, invariants,
- after, trans);
- oldivs = NULL;
- invariants = NULL;
+ &remove_ivs,
+ after, trans, &lambda_obstack);
+ modified = true;
+
+ if (dump_file)
+ fprintf (dump_file, "Successfully transformed loop.\n");
+
+ free_and_continue:
+ obstack_free (&lambda_obstack, NULL);
free_dependence_relations (dependence_relations);
free_data_refs (datarefs);
+ VEC_free (loop_p, heap, nest);
}
+
+ for (i = 0; VEC_iterate (gimple, remove_ivs, i, oldiv_stmt); i++)
+ remove_iv (oldiv_stmt);
+
+ VEC_free (tree, heap, oldivs);
+ VEC_free (tree, heap, invariants);
+ VEC_free (gimple, heap, remove_ivs);
+ scev_reset ();
+
+ if (modified)
+ rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa_full_phi);
}
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